In the disclosure of the present invention reference is mostly made to the treatment of diabetes, however, this is only an exemplary use of the present invention.
The most common type of injection devices adapted to receive a drug filled cartridge and expel a dose therefrom are generally pen-formed and utilizes a so-called cartridge holder adapted to receive and mount a cartridge in the device. Correspondingly, most pen-formed drug delivery devices comprises a generally cylindrical cartridge holder for receiving and holding a generally cylindrical drug-filled cartridge in a mounted position, the cartridge comprising a proximally facing and axially displaceable piston, and a main body with a housing in which a drug expelling mechanism is arranged, the mechanism comprising an axially displaceable piston rod adapted to engage the piston of a mounted cartridge to thereby expel a dose of drug from the cartridge. Between the cartridge holder and the main body a connection means is provided allowing a user to remove the cartridge holder from the main body and reattach it when a used cartridge has been exchanged with a new cartridge. The cartridge is in most cases inserted in the cartridge holder by axial movement through a proximal opening, see e.g. WO 2011/124631, EP 0 937 474 and WO 2011/092326. The connection means may be in the form of a threaded connection or a bayonet coupling. Depending on the design of the drug delivery device the piston rod has to be moved proximally (i.e. “reset”) by rotation when an empty cartridge is exchanged with a full cartridge, or the piston rod can be reset by being pushed axially, e.g. by unlocking the piston rod when the cartridge holder is removed from the main body, this as disclosed in for example US 2009/0275914, WO 2011/051366 and WO 2011/154482. The latter document discloses a drive mechanism with a stop member, a drive member and a rotation member, wherein either the stop member or the rotation member may be axially locked the other two being axially displaceable when operated between the resetting and operational state.
Alternatively, the drug delivery device may comprise an integrated (i.e. for the user non-removable) cartridge holder adapted to axially receive a cartridge through a distal opening. Such a device is often named “front loaded”, see e.g. WO 2004/020026 and US 2011/152822. The cartridge holder may be provided with gripping means adapted to hold and release an axially inserted cartridge.
Having regard to the above, it is an object of the present invention to provide a drug delivery device adapted to receive a drug-filled cartridge in a simple and effective way, the arrangement being to a high degree user-friendly, accurate and reliable.